Generally, power supply regulators typically comprise linear (series pass) and switching-type power supply regulators. Each type has distinct performance characteristics best applied in somewhat different applications. The older and better known linear regulators provide the necessary transient response to respond to rapid changes in power supply load conditions. However, the series pass elements therein typically are wasteful of power, even when optimized to provide a single (non-variable) output potential.
Alternatively, the switching regulator provides the highest level of regulator efficiency, at the expense of a slower response to varying load conditions. Again, while the regulator circuit response time may be optimized for a particular, non-varying output potential and range of load fluctuations, there remains a limiting minimum response time under which the switching regulator is unable to adequately respond.
Limitations of the above-described two classes of power supplies are further exacerbated when the requirement is imposed that the power supplies provide a selectively variable range of output potentials over a range such as 0 to 20 volts. The wide range of output potential makes optimization of either circuit difficult and provides the lowest efficiency of the linear regulator when the lowest range of voltages is selected.